Thyroid Disease Flashcards
The impact of amiodarone on thyroid
amiodarone is used in AF rate control (pharmacological conversion)
Thyroid axis
Hypothalamus TRH
Anterior Pituitary gland TSH
Thyroid T3 and T4
negative feedback on the hypothalamus and anterior pituitary
*anterior pituitary senses when T3 and T4 are low and secretes TSH in response.
Hyperthyroidism /
thyrotoxicosis
Very high T3 and T4, low TSH
subclinical hyperthyroidism
Subclinically low TSH - normal free T4 and T3
Thyrotoxicosis symptoms
nervousness increased sweating heat intolerance palpitations fatigue weight loss tachycardia dyspnoea weakness tachycardia skin changes tremor goitre eye changes AF
Reasons for thyrotoxicosis
2
Hormone overproduction - Grave's - Toxic multinodular goitre - Toxic adenoma - Iodine induced - Increased TSH secretion lots of nodules secrete thyroid hormones autonomously.
Excess hormone release
stimulation from a viral thyroiditis
- Subacute thyroiditis (sore throat, fluey, seen after COVID-19) * self-resolving*
- Postpartum thyroiditis: 6M of giving birth, treat symptoms but self-resolves.
Thyrotoxicosis investigation
Anti TCH antibodies (Graves)
if negative = Thyroid uptake scans
toxic multinodular goitre: black spots show uptake of the technician. (highly active nodules)
thyroiditis: less uptake
toxic adenoma: one dark uptake.
Grave’s disease clinical features
- Grave’s ophthalmopathy
- may need decompressive therapy
- Thyroid bruits (hold breath and listen to their thyroid. can hear a diffuse increase in blood supply/vasculature)
- Pretibial myxoedema on the shins
- Thyroid acropachy- digital clubbing, soft tissue swelling of hands and feet, periosteal reaction
TSH receptor antibodies + (anti TCH antibodies)
Grave’s management
medical mx
- medical therapy: carbimazole or propylthiouracil 12-18 months then withdrawal (they have an anti-inflammatory effect too) high dose carbimazole then replace blocked with levothyroxine or titrate
MOA.
- inhibit oxidation of iodide in the thyroid which blocks the formation of the thyroid hormone.
- PTU stops T4 to T3.
carbimazole 20-60mg / day
PTU 200-800mg/day
Reassess in 4 weeks and slowly reduce once euthyroid
maintain 5-20mg or 100-400mg/daily
Grave’s mx
radioactive iodine
- radioactive iodine (takes 1-6 months to work) swallow a capsule of iodine.
cannot have contact/share bed after the iodine for 4 weeks.
can exacerbate already bad eye disease (give steroids around the treatment or wait for the eye disease to improve)
Carbimazole and PTU adverse reactions
! adverse reactions ! agranulocytosis: rash, fall in blood count. if severe, sore throat, unexplained bleeding stop taking carbimazole and get an urgent blood count. hepatitis / liver necrosis thrombocytopenia vasculitis
! do not conceive
Carbimazole and PTU adverse reactions
! adverse reactions ! agranulocytosis: rash, fall in blood count. if severe, sore throat, unexplained bleeding stop taking carbimazole and get an urgent blood count. hepatitis / liver necrosis thrombocytopenia vasculitis
! do not conceive
Other medical therapy for hyperthyroidism
pre operatively
Lugol iodine agents
Dexamethasone 2mg 6hrly
beta blocker (propanol 20-80mg every 6-8hrs)
symptoms failed thionamide therapy agranulocytosis uncontrolled dangerous effects radioiodine or surgery
Treatment for Grave’s opthalmopathy
Mild generally resolves spontaneously- artificial tears, dark glasses, lubricants and taping at night
Glucocorticoids (40-50mg/day wean rapidly)
External beam radiation
Steroid sparing agents (methotrexate)
Rituximab
Surgical compression
Toxic Multi Nodular Goitre / Adenoma
treatment
Radioiodine first line treatment (aim for euthyrodisim)
Thionamides
Surgery (only if concerns for cancer or large goitre is causing compressive symptoms)
Thyroiditis
post viral / post partum
beta blockers for symptoms
- NSAIDS
- rarely glucorticoids
thionamides frequently make hypothyroid
frequently monitor for hypothyroidism
Thyroid storm (thyrotoxic crisis) clinical features
Rare but life threatening
Untreated / incomplete thyrotoxicosis
Poor complacence to meds, exacerbated by DKA, surgery, truama, infection
Overdrive of metabolism
Tachy-arrhythmias, pulmonary oedema, CCF, psychosis, severe abdominal pain, nausea, shock and coma
Management of thyroid storm
PTU 300-400mg 4 hrly Dexamethasone 2mg 6hrly Iodine 5-10 drops 6hrly Beta blocker Supportive - cooling
Hypothyroidism features
Low T4 and T3
Raised TSH
subclinical high TSH, low/normal T3 and T4
Hashimoto - anti thyroid peroxidase antibodies (anti-TPO)
more commonly found in females
Primary hypothyroidism (causes)
Congenital hypothyroidism (mutations)
Primary hypothyroidism
- hashimoto (autoimmune)
- iodine deficiency
- drugs (lithium, amiadorone, interferon)
- thyroid infiltration (haemchromatosis)
transient hypo-thyrdoidism
post thyrotoxicosis treatment
central hypothyroidism (pituitary disorders)
resistance to thyroid hormone (rare form, high levels of T3 and T4 but hte peripheral tissue is not responding to them)
symptoms of hypothyroidsim
tired, dry skin, cold intolerance, increased weight, constipation, difficulty concentrating, slowed thoughts
delayed ankle reflex, bradycardia, peri orbital puffy, coarse skin
(ankle jerk reflex in examination)
Mx of hypothyroidsm
levothyroxine (converted into T3)
1.6 ug/kg
take on empty stomach
check Ca carbonate, ferrous sulphate and cholestyramine
avoid iron or calcium supplements
aim for TSH in 1.0 mU/l
T3 (liothyroinine) short half life so very difficult to monitor.
initially commence on levothyroxine and review in 3-4 weeks. dose of therapy may need adjusting. if stable TSH is achieved then check 4-6 monthly and then annually.
Mx of hypothyroidsm
levothyroxine (converted into T3)
1.6 ug/kg
take on empty stomach
check Ca carbonate, ferrous sulphate and cholestyramine
avoid iron or calcium supplements
aim for TSH in 1.0 mU/l
T3 (liothyroinine) short half life so very difficult to monitor.
Combination of T4/T3 treatment
initiated in secondary care? look this up
Thyroid nodules and cancer
Lumps on self-palpation on thyroid
Neck/Carotid US, MRI and CT picks up incidental nodules
60% have nodules, 5% turns out to be carcinoma
Thyroid cancer types
papillary thyroid carcinoma (younger)
follicular thyroid carcinoma
lymphoma
sarcoma
(What is the difference?)
Amiadorone and thyroid
anti-arrhythmic drug given for rate control of AF
potent drug, very long half life (weeks-months)
can increase T4 and TSH (hyper)
can inhibit D1 and D2 (hypo)
can precipitate autoimmune hypothyroidism of GRav’e’s
amiadorone induced thyrotoxicosis types
type 1: susceptible gland (multi nodular goitre)
type 2: drug induced destructive thyroiditis (destruction) (manage with steroids)
treat: carbimazole, glucocorticoids, surgery.
pregnancy and the thyroid
pregnancy impacts thyroid physiology
foetus needs thyroid hormone from the placenta
rise in HCG impacts maternal thyroid hormone levels.
hypothyroidism in pregnancy
TSH >2.5 free T4 is low
(makes sure the baby has enough to develop normally)
subclinical hypothyroidism TSH 2.5-10 with normal free T4
hypothyroidism- risk of premature birth, low birth weight and miscarriage
treat with thyroxine
1st trimester 0.1-2.5mu/l
2nd trimester: 0.2-3.0mu/l
third trimester 0.3-3.0mu/l
carbimazole and PTU in pregnancy
aplasia cutis- congenital malformation of the scalp
choanal atresia / oesophageal atresia
beta blocker: lower dose for shortest duration
PTU has less congenital malformations, can cause hepatotoxicity. only given in 1st
check these slides over (foundation week thyroid disease lecture)
carbimazole and PTU in pregnancy
aplasia cutis- congenital malformation of the scalp
choanal atresia / oeseophageal atresia
beta blocker: lower dose for shortest duration
PTU has less congenital malformations, can cause hepatotoxicity. only given in 1st
check these slides over (foundation week thyroid disease lecture)
sub-clinical thyroid disease
subclinical hypo: raised TSH, normal T4, T3
subclinical hyper: low TSH, normal T4, T3
anapaestic carcinoma of the thyroid
relatively uncommon tumor
most commonly occurs in the elderly
locally invasive, causes recurrent laryngeal nerve palsy secondary to hoarseness, dysphagia and stridor due to direct airway invasion
metastasises to local lymph nodes and then to distant sites.
poor prognosis
grave’s thyroid
slight enlargement
diffusely and smoothly enlarged
hypervascularity may result in an audible bruits
simple colloid goitre
smoothly enlarged thyroid gland, normal thyroid function test. mainly due to iron deficiency / puberty or pregnancy (thyroxine demand increase)
MEN type 2
HTN, headaches, raised urinary catecholamines, adrenal mass on CT indicates pheochromocytoma.
raised PTH and Ca2+ suggests parathyroid hyperplasia
